Rheostat



(No Model.)

A. J. SHAW. BHEOSTAT.

No. 515,254. P5555555 Feb. 20, 1894.

UNITED STATES PATENT OEEIcE.

ALTON J. SHAWV, OF MUSKEGON, MICHIGAN.

R-H EOSTAT.

$PECIFIGATION forming part of Letters Patent No. 515,254, dated February20, 1894. Application filed October 13, 1893. Serial Ila 438,087. (Nomodel.)

To all whom it may concern.-

Be it known that I, ALTON J. SHAW, a citizen of the United States,residing at Muskegon, in the county of Muskegon and State of Michigan,have invented certain new and useful Improvements in Rheostats, of whichthe following is a specification.

My invention relates to resistance devices for use in electrical work,and has for its object the production of a cheap, durable and compactdevice, capable of withstanding the action of moderate currents.

The invention is in the nature of a modification of that set forth inanother application filed in my name October 12, 1893, and hearingSerial No. 487,926. As the resistance card, block, or section hereindescribed may be used singly, as well as in a group or series, and asthe manner of grouping, connecting, &c., is fully set forth in saidapplication, I shall show and describe only one such section in thepresent case.

In the drawings,-Figure 1 is a side elevation; and Fig. 2, a transversesection of my improved resistance card or section, Fig. 1 showing alsothe supporting body, the contact block, and the manner of securing thecontact block and card to the supporting body.

In said figures, A indicates a supporting body, which may be of slate,vulcanized fiber, or other material capable of withstanding hightemperatures, and having good insulating properties; or it may be asubstance incapable initself of acting as an insulator, but providedwith means of insulation from the parts carried by it. In every case oneor the other provision for insulation must be made.

B indicates a frame, preferably of a sub stantially rectangular form andcomprising a top bar a, side bars I) b, and bottom bar 0, which lattermay, however, be omitted, provided the side bars be made sufficientlyrigid. In cross section, the side bars are triangular or wedge-shaped,the angles being removed, and the apices facing each other, as shown inFig. 2. At or near the lower end of each side bar I) there is formed aswell or projection, cl, which precludes the escape of the wire or bandwhich forms the resisting conductor,

should said wire become loosened through expansion or otherwise. Theframe B is provided with an insulating covering or envelope, advisablyof enamel such as is commonly employed for metallic culinary vessels andutensils, that used upon the so-called granite-ware being very welladapted to the purpose. Asbestus, mica, or other heat-resisting electricinsulator may be employed instead of enamel, but not so satisfactorily,all things considered.

0 indicates a wire, band or strip of metal or alloy, which has one endmechanically and electrically connected with the frame B. Thisconnection may be conveniently made by drilling a hole into the frame B,and inserting the end of the wire therein, wedging, screwing, riveting,or brazing the same in place, or passing the wire through the hole andthen twisting it about itself or about the frame, or otherwise made fastto insure its retention. The attachment of the wire is ad- Visably madeat or near the upper end of one of the side bars I), as in Fig. 1. Afterthus securing the wire, it is wound about the frame in separated foldsor courses, as illustrated in Fig. 1,the separation being sufiicient toafford good ventilation, and, if bare wire be used, sufficient also toprevent short circuiting or leaping of the current across the spacesfrom fold to fold. The winding is continued from one end of the frame 13to the other, or such portion thereof as may be necessary to give therequired resistance'to the section, and just before leaving the framethe wire or band is twisted about itself, as shown in Fig. 1, to preventunwinding. After winding the wire upon the frame, the whole is or may bedipped into an enamel bath, the enamel being subsequently hardened bybaking or otherwise. The enamel serves not only to secure the wires inplace, but also insulates them so that there is no liability ofshortcircuitiug in the event of the wires being crossed by anyconducting material. The thickness of the side bars I) b will besufficient to preclude the leaping of the current across from folds atone side of the frame B to those on the opposite side thereof. Thetriangular form of the side bars gives adequate strength with relativelylimited bearing surface for the wire, which is consequently thoroughlyventilated throughout. By rounding off the corners or angles I lessenthe liability of the enamel being broken or chipped off.

D indicates a contact block with which the frame B is mechanically andelectrically connected by screws or equivalent fastenings E, passingthrough the block D and support A, and entering holes formed in the bara of frame B. An additional screw passing through support A and enteringbar a, is also shown,

- but that has a special function and is claimed to insulate theframe-and the band, except at a single point where the twoareelectrically connected.

3. A resistance card or body consisting of a frame B, having triangularbars, an insulating covering for said frame, and a metallic baud woundupon said frame over the insulation but electrically connected with saidframe at one point.

4. In combination with frame B having projections d, wire 0 wound aboutsaid frame and electrically connected therewith at one point, andinsulating material interposed between the frame and the body of thewire.

5. In combination with supporting body A,

frame B, and its band C, contact block D,

and fastenings extending from the block D to frame B and servingelectrically to connect the same.

In witness whereof I hereunto set my hand in the presence of twowitnesses.

ALTON J. SHAW.

Witnesses:

J. G. EMERY, J r., T. O. AKIN.

